1. Field of the Invention
The present invention relates to a medical device for delivering a substance to a vascular lumen. In particular, the invention relates to a catheter for delivering and/or withdrawing a therapeutic substance to a location within a vascular lumen.
2. Related Art
Percutaneous transluminal coronary angioplasty (PTCA) is a procedure for treating heart disease. Typically, a catheter assembly having a balloon portion is introduced percutaneously into the cardiovascular system of a patient via the brachial or femoral artery. The catheter assembly is advanced through the coronary vasculature until the balloon portion is positioned across the occlusive lesion. Once in position across the lesion, the balloon is inflated to a predetermined size to radially compress the atherosclerotic plaque of the lesion against the inner wall of the artery to dilate the lumen. The balloon is then deflated to a smaller profile to allow the catheter to be withdrawn from the patient""s vasculature.
Restenosis of the artery commonly develops over several months after the procedure, which may require another angioplasty procedure or a surgical by-pass operation. Restenosis is thought to involve the body""s natural healing process. Angioplasty or other vascular procedures injure the vessel walls, removing the vascular endothelium, disturbing the tunica intima, and causing the death of media smooth muscle cells. Excessive neointimal tissue formation, characterized by smooth muscle cell migration and proliferation to the intima, follows the injury. Proliferation and migration of smooth muscle cells (SMC) from the media layer to the intima cause an excessive production of extra cellular matrices (EM), which is believed to be one of the leading contributors to the development of restenosis. The extensive thickening of the tissues narrows the lumen of the blood vessel, con stricting or blocking blood flow through the vessel.
To reduce the chance of the development of restenosis, therapeutic substances are administered to the treatment site. For example, anticoagulant and antiplatelet agents are commonly used to inhibit the development of restenosis. To supply an efficacious concentration to the target site requires a systemic administration of such medication in quantities which often produces adverse or toxic side effects for the patient. Local delivery is a preferred method of treatment in that smaller total levels of medication are administered in comparison to systemic dosages, but are concentrated at a specific site. Local delivery, thus, produces fewer side effects and achieves more effective results.
The present invention provides a catheter for delivery of a therapeutic substance to a target location in a patient""s vasculature. The catheter supplies an efficacious concentration of the therapeutic substance to the target site, which reduces the total levels of medication required to be administered to patients relative to typical systemic dosages. The concentrated delivery of the therapeutic substance produces fewer side effects and achieves more effective results.
In one aspect of the invention, the catheter includes an injection port at or near the distal end thereof and a surface for applying a force to cause the injection port to move between a first position and a second position in the first position the injection port is substantially aligned with a central axis of the catheter. Upon application of the force, the injection port moves between the first position and the second position perpendicular to the central axis of the catheter. Advantageously, an additional force can be applied which causes the injection port to move to a third position away from the central axis of the catheter and into a wall of the vasculature. Advantageously, the injection port is a hollow needle disposed at the end of a substance delivery lumen.
In another aspect, a method is provided for delivering medication to a patient. The method includes delivering at least one injection port to a location within a human vasculature. The injection port is coupled to a substance delivery lumen. The injection port is moved between a first position and a second position to inject medication into the patient through the substance delivery lumen and the injection port.